1. Field of the Invention
The present invention relates to tomography using an electromagnetic wave (frequency thereof is equal to or more than 0.01 [THz], and equal to or less than 100 [THz]) (such as a terahertz wave (frequency thereof is equal to or more than 0.03 [THz], and equal to or less than 10 [THz]), for example).
2. Description of the Prior Art
There has conventionally been the computed tomography (CT) as a method for obtaining tomographic information on a device under test. This method conducted while a generator and a detector of the X ray are used is referred to as X-ray CT. With the X-ray CT, it is possible to acquire tomographic information on a human body in non-destructive and non-contact manner.
However, it is difficult for the X-ray CT to detect internal states (such as defects and distortions) of industrial products constructed by semiconductors, plastics, ceramics, woods, and papers (referred to as “raw materials” hereinafter). This is because the X-ray presents a high transmission property to any materials.
On the other hand, the terahertz wave properly transmits through the raw materials of the industrial products described above. Therefore, the CT carried out while a generator and a detector of the terahertz wave (referred to as “terahertz CT” hereinafter) are used can detect internal states of the industrial products. Patent Document 1 and Non-Patent Document 1 describe the terahertz CT.    (Patent Document 1) U.S. Pat. No. 7,119,339    (Non-Patent Document 1) S. Wang et al., “Pulsed terahertz tomography,” J. Phys. D, Vol. 37 (2004), R1-R36